New 42” Camera Status

November 20, 2009

Ted Dunham, Peter Collins, Tom Bida, Georgi Mandushev, and

Saeid Zoonemat Kermani

Outline• General Comments• Plate scale, field of view, field orientation (Peter)• Read times, gain/noise/linearity/full well• Vignetting by the filter edges• Fringing in the I band• > Shutter performance in terms of flat fields and

stellar photometry• Focus vs. filter and focal plane tilt (Tom)• > Throughput, color terms (Georgi)• Odds and Ends• LOIS/LOUI arrangement• Demonstration of camera operation in the lab

General Comments• CCD: 4Kx4K 15 micron e2v CCD231

– Physically larger than the SITe by 30/24 = 1.25x– Uses the same filters; they limit the field of view– Filter wheel common to SITe; camera switch is involved

• Can use 1, 2, or 4 amplifiers• Pixel size suggests 2x2 binning most common use

case. All engineering work at 42” done this way.• Dynamic range of the CCD pushes 16 bits• Uses a sliding blade type of shutter• Uses a Cryotiger mechanical cooler, no LN• Uses the new LOIS/LOUI control software system• Remote/robotic operation possible in principle

Plate scale, Field size & Orientation• Scale

– Move: 0.74”/px• 2x2 binned

– Plate Solution:0.7402 to 0.7404”/px

– Rotation: -0.29 degrees, but will be different next time.

• Field of view– 25.3 arcmin,

vignetted– ~22 arcmin

unvignetted– SITe is 20.2 arcmin

• Many possible amplifier combinations.– Strip scanning uses E-W columns

– Possible, but not described here

• Default is single A amplifier• Single: A B C D ((0,0) in lower left)

• Two: AB CD BD (AC not possible)

• Four: ABCD or ALL

Display Orientations

N N

N N

EEEE

N

E N

E N

E

N

E

• Goal: Allow choice of slow (quiet) and fast (noisy), details TBD

• More distant goal: Allow two full well options– Right now we support “Mode 1”, limited by the output node

capacity of ~200Ke with low noise– Plan to support “Mode 2”, limited by either the pixel capacity

(~350Ke unbinned) or the output node capacity of ~600Ke with higher noise.

• Current state is that we’ve only done one case (~1.8 us/px) as shown next.

• Running too fast makes 4 amplifiers not work - it overruns the fiber bandwidth of 2.5 Mpx/sec.

Gain, Noise, Speed, Linearity, & Full Well

Gain, Noise, Speed, Linearity, & Full Well

• Current Configuration Properties, full frame plus 50 columns of overscan

• Table below shows read times for various amplifier combinations. Doesn’t include display time!

Unbinned 2x2 binned

A 33.6 sec A 9.9 sec

AB or CD 17.6 sec AB or CD 5.4 sec

BD 17.3 sec BD 5.1 sec

ABCD 9.2 sec ABCD 2.0 sec

Gain, Noise, Speed, Linearity, & Full Well

• Gain & Noise

Amplifier C D

Gain (e/DN) 4.67 4.77

Noise (e) 5.4 5.3

Amplifier A B

Gain (e/DN) 4.82 4.62

Noise (e) 5.4 5.5

Gain, Noise, Speed, Linearity, & Full WellAmplifier A

1

10

100

1000

0.1 1 10 100 1000 10000 100000

Mean - Bias (ADU)

Noise per frame

R_DELAY=1R_DELAY=0

Funny things start to happen around 40000 ADU

Gain, Noise, Speed, Linearity, & Full WellAmplifier A Nonlinearity

-12.0%

-10.0%

-8.0%

-6.0%

-4.0%

-2.0%

0.0%

2.0%

4.0%

6.0%

0 10000 20000 30000 40000 50000 60000

Mean - Bias (ADU)

Normalized Nonlinearity (%)

R_DELAY=1

R_DELAY=0

Possible shutter calibration offset?

Vignetting by Filter

I Band Fringing• Fringing seen in this 100

sec I band image (OS160 on 091108 UT)

• 4.5% to 6.0% P-P amplitude

Shutter Performance: Flats• Took twilight flat pairs on 20091109 UT

– Shutter blades move in opposite directions– Exposure times ranged from 0.01 sec to 10 sec.

• Subtracted bias frames from each flat• Took the ratio of the pairs• Subtracted the DC value of the ratio

– Due to changing twilight sky brightness

• Looked at the images & slices through them• The shutter has a fixed motion pattern that is

fractionally larger at shorter exposure times.

Shutter Performance: Flats• 1 sec. exposure• ± 2% full scale• ± 0.2% nonuniformity

including the drift part

Shutter Performance: Flats• 100 msec. exposure• ± 2% full scale• ± 0.8% nonuniformity

Shutter Performance: Flats• 10 msec. exposure• ± 10% full scale• ± 7% nonuniformity

Shutter Performance: Flats

• Summary of flat pair test results

P-P error (%)

0.1

1

10

100

0.01 0.1 1

Exposure time

P-P error

P-P error (%)

Shutter Performance: Stars

• On 20091109 UT took exposures in a 1,2,5 sequence from 10 ms to 20 sec on part of SA 114-176

.01 132 143

.02 133 144

.05 134 145

.10 135 146

.20 136 147

.50 137 1481.00 138 1492.00 139 1505.00 140 15110.00 141 15220.00 142 153

Analysis not quite finished

Look at saturation behavior with IRAF on 139

Focus vs Filter and FP Tilt• Tom did this analysis• There isn’t a significant CCD tilt• There is significant radial focus variation across the

CCD– Correct magnitude for RC field curvature– Opposite sign! Don’t understand this.– Significant filter-to-filter differences. Don’t understand

these either.

• Best to focus partway to the edge– Split the difference on the center-to-corner focus– Focus deviation in this case ~ ± 15 steps = ± 0.6 arcsec

• V,R,I have about the same focus; B is ~30 steps more positive.

Focus vs Filter and FP Tilt• B and V• Contour interval is 5 steps

785815

Focus vs Filter and FP Tilt• R and I• Contour interval is 5 steps

820 810

Throughput

• Not done. Need to look at spectrophotometric standards and put together a model of system transmission for this.

Color Terms

Odds and Ends• Funny saturation behavior

– Probably related to node capacity limit instead of charge capacity in the pixel

• Need to fix the DC restore problem• Multiple amplifiers have issues with the

“pipeline” pixels in the Leach controller.• Low-level dark streaks behind saturated stars• Frame-transfer HIPO data acq. Modes

available in principle

Work Items• Finish up gain/noise/speed/linearity in the lab

– Choose the slow and fast cases

• Finish up the shutter test on stars - analysis• Examine the possible shutter calibration issue• Look at the overall throughput - analysis• New big disk for hall; second display probably

needed using a Sewell USB video adapter.• A few mechanical things for Ralph.• Control software mods

– Pretty long list right now– Add more based on real observing experience

LOIS/LOUI Arrangement: I• Split off LOIS’ GUI function, moved to LOUI• Reliability greatly improved• Three main programs:

– LOIS: Retains most control functions• TCL scripting function unchanged

– LOUI: GUI, written in java• Available for multiple platforms• Two image display options: ds9 & LOUI internal

– Active MQ message broker, not obviously visible to the observer.

• Can run almost anywhere.

LOIS/LOUI Arrangement: II

Camera Controller(on telescope)

Sun computer(nasa42)

Runs LOISRuns broker

Move

LaptopCan run LOUI too

Mac Mini (hall)

Runs LOUIFiber

Serial

Network